• Question: why is the whole universe STILL expanding .. why cant it stop ?

    Asked by sodiumpolyacrylate to David, James, Mike, Suze, Will on 15 Jun 2011. This question was also asked by ayishae.
    • Photo: James Marrow

      James Marrow answered on 14 Jun 2011:

      It might!

      There are models that predict the expansion of the universe, and depending on the assumptions in the models (“assumption” is the phrase scientists use instead of “best guess”), the universe will either continue to expand, or begin to shrink again! Some even think it will do this over and over again.

      However, I think most astronomers now think that it won’t shrink, and will indeed continue to expand. There’s nothing to stop it.

    • Photo: Suze Kundu

      Suze Kundu answered on 14 Jun 2011:

      I’m so glad that someone answered this! I know that it is expanding, and I know that it could reach a limit, but I’m not sure why… I thought that it might be something to do with the initial Big Bang.

      If you’re still curious and want a better answer, let me know, and I’ll ask my friend, Space Boy (yes, he’s real, but sadly no, that’s not his real name. I’m trying though 😛 )

    • Photo: David Ingram

      David Ingram answered on 14 Jun 2011:

      Whether it stops or not depends on the mass of dark matter in the universe. Most astronomers think there isn’t enough dark matter for gravity to win and the universe to start shrinking.

    • Photo: Mike Dodd

      Mike Dodd answered on 15 Jun 2011:

      It’s still expanding because of the force of the big bang and also dark matter. But I don’t no why! Sorry

Comments

  • Photo: Suze

    Suze commented on :

    OK, I have an amazing answer, straight in from Space Boy, as follows (he is wonderful! x)

    Space Boy says:
    Yes measurements suggest the Universe is expanding. This is weird. People expected that the expansion of the Universe would be slowing down as the gravity of the all the stuff in it started to beat what was left of the energy of the Big Bang. It turns out not only is the expansion of the Universe not slowing down, it is actually *acceleratingMATOMO_URL

    Astronomers first discovered this by using something called a “standard candle”. Basically there is a type of exploding star called a Type 1a supernova. Astronomers believe that these supernovae always exploded with exactly the same brightness. If you can measure its apparent brightness with a telescope you can tell how far away it is (and the galaxy it is in) by how much dimmer it is compared to how it should be if you were right next to it.

    When astronomers collected details of a lot of these supernovae they found that when they compared these distances (found in the way above) to how fast the galaxies were moving away from us, the expansion of the Universe was speeding up and not slowing down.

    This is where “dark energy” comes in. Astronomers have to invent this mysterious entity as the culprit that is driving galaxies apart at an ever increasingly rate. Trouble is no-one knows what it is. All they know is that is makes up 73% of all the energy in the Universe. Basically most of the Universe is missing down the back of some cosmic sofa!

  • Photo: Suze

    Suze commented on :

    By the way, his ‘real’ name is Colin Stuart (at least until Space Boy sticks), and he’s all about astronomy. Look him up. He’s my favourite 🙂